Caterina Sforza was born in Milan, Italy in 1463, the illegitimate daughter of Galeazzo Maria Sforza by his mistress Lucrezia Landriani. Her mother was always concerned about her welfare, being close to her in the most crucial moments of her life. She received a humanistic education at the Sforza court, which was frequented by writers and artists, after being adopted by Galeazzo's wife Bona of Savoy in 1468, and she acquired a lifelong passion for hunting while hunting with her father at Galliate and Cusago. In 1473, she was betrothed to marry Girolamo Riario, and they consummated their marriage in 1477, when she was fourteen and her husband was thirty-four. Her husband banned her from meddling in politics in Rome, but she became one of the most respected and loved female aristocrats in the city, as she was well-known for her grace and beauty. In 1480, she was rescued from a small island in Romagna by the Florentine nobleman Ezio Auditore da Firenze, who took the stranded Sforza to shore on a gondola. Sforza ordered for the captain of a Venetian ship to allow Auditore on board without a pass, showing her gratitude. The two flirted with each other, and she invited Ezio to come to Forli any time. Leonardo da Vinci warned Ezio that Sforza was powerful and dangerous, but Ezio took a liking to her.
Battle of Forli
In 1484, the death of Riario's uncle Pope Sixtus IV changed everything, as several rebellions broke out. The Riario family's residence in Rome was destroyed by rioters, and the pregnant Caterina rode to the Vatican to defend it with cannon fire and soldiers. Later that year, Caterina and her family moved to the city of Forli in Romagna. In 1485, the city government ran out of money, and a tax increase led to popular unrest. In 1488, Caterina hired Checco and Ludovico Orsi to murder her husband, as he had been a lousy father, boring in bed, and a pain to her. However, the Orsi brothers decided to seize power for themselves, and Caterina Sforza requested the assistance of Ezio Auditore in rescuing her captured children and retaking the city. When the Orsis threatened to kill her children, Sforza lifted her dress to show her panties, telling them that she had the instruments to make more. Auditore succeeded in rescuing the children, and he managed to slay Checco shortly after.
Countess of Forli
Caterina was confirmed as the lone ruler of Forli on 30 April 1488, serving as regent for her young son Ottaviano Riario. She had all members of the Orsi conspiracy imprisoned, and houses owned by the conspirators were razed and their valuables given to the poor. Sforza controlled her realm's spending by decreasing or eliminating taxes, and she managed Forli and Imola's diplomacy. Things changed when Pope Alexander VI came to power in 1492, the same year as Lorenzo de Medici's death. The French invaded Italy as Milan and Naples engaged in a rivalry in 1494, and Caterina chose to side with Naples and the Pope against Ludovico il Moro of Milan and King Charles VIII of France. The Neapolitans did not help her defend her realms against the first French attack, so she later switched sides and decided to help the French against the Pope and Naples. In 1497, she married Giovanni il Popolano, the cousin of the late Lorenzo the Magnificent, and they planned to defend Forli from the Republic of Venice and the Borgias. However, Giovanni's death in 1498 left Caterina alone in the struggle against the Borgias, and Papal general Cesare Borgia conquered Milan on 6 October 1499, Imola on 24 November 1499, and Forli on 19 December 1499. On 25 December, as Forli's citadel was being besieged by Papal troops, Caterina and a few soldiers snuck out to join Ezio and his uncle Mario Auditore at Monteriggioni in Tuscany, and they assisted in the defense of the city from the Borgia army. However, she was captured by Juan Borgia the Elder during the fall of the city, and she was imprisoned in the Castel Sant'Angelo until 1501, when Ezio freed her during a failed attempt to assassinate the Pope and his son.
Caterina knew that she was useless to the anti-Borgia cause without holding any lands, so she decided to return home to take care of her children. Sforza attempted to leave without anyone noticing, but Ezio confronted her, and she told him to unite the anti-Borgia resistance in Rome to overthrow the Pope. She then left on horseback, returning to Forli. She would later attempt to convince Pope Julius II to return her lands in Forli, but the people of Forli objected, and she died of pneumonia in Florence in 1509.